1. Field of the Invention
The present invention relates to metal cation-doped covalent organic framework derivatives for hydrogen storage and uses thereof, more particularly, to a novel hydrogen storage material with enhanced hydrogen storage capacity prepared by doping an organic framework material with light metal cations and a method of using the same for hydrogen storage.
2. Description of the Related Art
Fossil fuels have cornered more than 90% of traditionally used energy needs and it is known that they are unable to be re-generated, limited in their reserves and importantly cause environmental problems due to pollutants such as carbon dioxide gas generated by combustion.
As a clean energy resource, hydrogen energy has recently received attention as an alternative to such fossil fuels. For fuel battery systems using hydrogen, there are advantages in that they can infinitely generate hydrogen from water thereby eliminating concern for exhaustion of natural resources and they never discharge environmental pollutants such as CO2 as hydrogen is used.
However, the above fuel battery systems need a hydrogen storage medium in order to use hydrogen, and the DOE (Department of Energy) in the U.S.A. has proposed applicable standard values for hydrogen storage materials. Extensive research and investigation into development of a hydrogen storage medium which fulfills the standard values proposed by the DOE is recently proceeding on the basis of carbon nanotubes, inorganic framework materials, metal hydride compounds, etc.
In 2007, Yaghi research group reported three-dimensional covalent structural organic frameworks (3D COFs), which comprise covalent bonds of unit organic molecules to form triangular and tetrahedral structures. See Science, 316, 268 (2007).
It was introduced that four kinds of COFs disclosed in the above reported document have pores with size of 1 to 2 nanometers and thermal stability even at more than 350° C. COFs with suitable pore structure and surface area have the potential to be used as storage materials, filters or the like.
However, there are undesirable problems in conventional technologies for hydrogen storage materials, which have not satisfied the applicable standard values for hydrogen storage materials proposed by the DOE, since, for example, carbon nanotubes or inorganic frameworks are combined together by physical adsorption with very low binding energy between the storage materials and hydrogen molecules such that they show very low hydrogen storage capacity at room temperature under ambient pressure, or, metal hydrogen compounds are combined together by chemical adsorption with very high binding energy so that they require alternative energy for discharging hydrogen.